Pre-insulated roofing and wall panels have come into wide use for the weathering and insulation of many types of building and are commonly referred to as composite or bonded insulation panels or sheets. In the case of composite panels, such as disclosed in U.S. Pat. No. 3,464,831, foam plastics material is injected between two layers of metal or membrane. A bonded insulation panel is a profiled metal sheet with a layer of foam plastics insulation material bonded to the underside.
Several forms of jointing sections, including plastics and metal sections, have been utilised to join insulation panels side-by-side. These jointing sections have normally been provided for aesthetic reasons in that they have hidden the joints between panels. There is, however, a problem associated with such joints in providing an effective vapour seal which prevents warm moist air passing through the joint and condensing on the cold surface of the outer metal or plastics weathering sheet. When condensation occurs, the resulting liquid can drip through the joint into the building. Serious problems of condensation occur when voids in the construction are created as is the case in bonded panels.
Virtually all known pre-insulated sheets rely on foam plastics insulating materials which are dimensionally unstable and, when applied to metal sheets, the considerable differences in coefficients of expansion of the two materials lead to breakdowns in adhesion of the insulation to the metal sheets. A major disadvantage of foam plastics insulating materials is that they are thermally decomposable to liberate toxic and noxious fumes with emission of dense smoke.
The advent of pre-insulated composite or bonded panels had its origin in the difficulties of site-assembled insulated roofing and cladding. The site-assembled methods relied entirely on the expertise of the erector or installer and were subject to prevailing weather conditions. The problems of achieving effective insulation coupled with endeavours to avoid serious condensation promoted the development of factory insulated products.
U.S. Pat. No. 2,142,305 discloses gypsum panels having on each of two opposite edges complementary metallic elements. The gypsum panels are precast and may be reinforced by mineral fibres which are admixed with the liquid cementitious material prior to casting of the latter. The metallic elements are keyed to the opposite edges of the panels during the pouring of the cementitious material. The metallic elements extend the full length of the panel and are flanged at their longitudinal edges, with the flanges extending parallel to major faces of the panels and lipped at their free edges to key into the cementitious material when the latter is poured to cast the panels. The flanges are usually flush with the major faces of the panels but one or both of them may be embedded in the cementitious material so that it is not exposed on the outside of the slabs. The complementary shaping of the two metallic elements on opposite sides of a panel is intermediate the depths of the elements, i.e. at positions spaced from both flanges. In a modification of construction where one flange of each metallic element is flush with a major surface of the panel and the other is embedded, with the complementary shaping of the metallic elements intermediate the two flanges providing tongue and groove interengagement with adjacent slabs, a flange is not provided at the embedded edge of the metallic element shaped to provide a groove, and, instead the length of metal at the groove opening side remote from the flush flange is bent back and splayed relative to the flush flange.
The metallic elements are fast with the cast cementitious material in panels in accordance with U.S. Pat. No. 2,142,305. Thus there are cold bridges between the two materials with temperature transfers between the two materials.